Loudspeakers typically comprise an electro-magnetic motor and a diaphragm or cone. The audio driver comprises a voice coil and former that are configured to move in response to electrical signals received at the audio driver. The cone is attached to the voice coil and vibrates with movement of the voice coil to cause a pressure wave, which is heard as sound by a listener.
In order to reproduce sound accurately based on the received electrical signals, a cone should ideally have pure pistonic motion. Pistonic motion may be characterised by linear motion of the cone away from and towards a plane of the electro-magnet motor with zero or minimal deformation of the cone, either due to mechanical break up or standing wave patterns.
In addition, the cone should be permitted to move freely in response to movement of the voice coil and former. Damping compound may be added to the cone but this increases the mass of the cone, which restricts the free movement of the cone and therefore distorts and/or degrades the sound produced by the loudspeaker.